21787373 has 2 divisors, whose sum is σ = 21787374. Its totient is φ = 21787372.

The previous prime is 21787313. The next prime is 21787379. The reversal of 21787373 is 37378712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12411529 + 9375844 = 3523^2 + 3062^2 .

It is a cyclic number.

It is not a de Polignac number, because 21787373 - 2¹⁴ = 21770989 is a prime.

It is a super-2 number, since 2×21787373² = 949379244482258, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21787379) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10893686 + 10893687.

It is an arithmetic number, because the mean of its divisors is an integer number (10893687).

Almost surely, 2^21787373 is an apocalyptic number.

It is an amenable number.

21787373 is a deficient number, since it is larger than the sum of its proper divisors (1).

21787373 is an equidigital number, since it uses as much as digits as its factorization.

21787373 is an evil number, because the sum of its binary digits is even.

The product of its digits is 49392, while the sum is 38.

The square root of 21787373 is about 4667.6946129754. The cubic root of 21787373 is about 279.2982982219.

The spelling of 21787373 in words is "twenty-one million, seven hundred eighty-seven thousand, three hundred seventy-three".